1. Field of the Invention
This invention relates to an improved safety syringe device. More particularly, this invention relates to a safety syringe device having a shield and employing a tracking system for providing automatic retraction of a syringe needle within the shield after a one-time use of the device.
2. Discussion of the Related Art
Syringes that extend and retract within a shield, thereby providing protection against an inadvertent needle strike, are well known in the art. A syringe that is capable of automatically retracting a needle within a shield upon discharging fluid from the syringe is highly desirable to reduce the risk of needle exposure after the syringe has been used. Automatic retraction syringes have been offered in the art; however, an effective syringe has not been offered which permits the needle to be easily retracted into the shield when the liquid within the syringe has been completely discharged. Nor have the previous syringes been sufficiently inexpensive in production to permit their widespread adoption.
U.S. Pat. No. 5,980,494 (Malenchek et al.) discloses a safety syringe device employing an automatic retraction feature for the syringe needle. The Malenchek et al. device includes a housing having a bore extending in an axial direction from its proximal end to its distal end. A vial is disposed within the housing bore and may be axially displaced between retracted and extended positions. The vial has a fluid receiving chamber for receiving a plunger extending between its proximal and distal ends. The vial also has a needle secured to its distal end that is in fluid communication with the vial chamber, and the needle is fully retracted in the housing bore when the vial is in the retracted position. The needle extends from the bore distal end when the vial is in the extended position. A positioning means, responsive to an initial vial axial displacement, releasably locks the vial in the extended position. The positioning means permits unlocking of the vial upon a subsequent vial axial displacement and further permits automatic displacement of the vial to the retracted position after the vial is unlocked. The positioning means includes grooves and ratchet teeth defined on the interior surface of the housing bore, a ratchet member disposed on the exterior surface of the vial and a ring disposed around the vial with camming tabs that engage the ratchet teeth of the housing and the ratchet member of the vial. The syringe disclosed in the Malenchek et al. patent is not reliable in operation and is very expensive to manufacture. Moreover, the design is not suitable for low cost mass production of the device.
An improved design of a safety syringe that provides easy and reliable automatic retraction of the syringe needle into the housing after liquid is completely expelled from the vial is therefore highly desirable.
An object of the present invention is to provide an improved safety syringe that is easy to manufacture, in machining of parts as well as assembly, and reliable during use. Another object of the invention is to provide a safety syringe that is suitable for low cost mass production.
A further object of the invention is to provide a safety syringe having a temporary locking position that maintains exposure of the needle outside of the shield during aspiration of fluid into its vial, and automatically retracts the needle to a locked position within the shield after fluid is completely discharged from the vial.
The aforesaid objects are achieved individually and/or in combination, and it is not intended that the present invention be construed as requiring two or more of the objects to be combined unless expressly required by the claims attached hereto.
In accordance with the present invention, an improved safety syringe includes a vial having a distal end configured for attachment with a vacuum needle, wherein the vial has at least one first protrusion and at least one second protrusion extending from an exterior surface of the vial. The second protrusion is circumferentially spaced a selected distance from the first protrusion along the exterior surface of the vial. The vial has a cavity defined between its proximal and distal ends, and the vial cavity is configured to telescopically receive a plunger at an aperture defined at the vial distal end. A ring is rotatably and slidably secured around the vial between the vial distal end and the protrusions. The ring has at least one tab projecting from an exterior surface of the ring, and the tab includes an engaging surface configured to engage with complimentary engaging surfaces on each of the protrusions.
A shield telescopically receives the vial and ring at an aperture defined at its proximal end. The shield also has an aperture defined at its distal end and a cavity defined between the proximal and distal ends and in communication with both apertures. The aperture at the shield distal end permits the vacuum needle, when attached to the vial, to extend from or retract into the shield cavity. An interior surface of the shield defines at least one channel configured to receive the tab of the ring. A resilient member is further placed within the shield cavity to bias the ring and vial toward the shield proximal end.
A first ridge and a second ridge are disposed on a raised portion of the shield interior surface adjacent the channel. The ridges face the shield distal end with a valley defined therebetween. The valley is configured to receive and hold the tab on the ring in a temporary locked position during aspiration of fluid into the vial. In addition to its axial bias, the resilient member may also rotationally bias the ring in a direction from the first ridge to the second ridge of the channel.
The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of specific embodiments thereof, particularly when taken in conjunction with the accompanying drawings wherein like reference numerals in the various figures are utilized to designate like components.